A transaction is a transfer of value between Bitcoin addresses that is included in the Blockchain. Bitcoin wallets hold secret data called a private key or seed, which is used to sign transactions, providing mathematical proof that they come from the owner of the wallet. The signature also prevents anyone, once the transaction is issued, from modifying the transaction. All transactions are broadcasted over the network and usually begin to be confirmed within 10 to 20 minutes, via a process called mining. One of the jobs of a bitcoin node is to verify that the incoming transactions are correct, that the data has not been falsified, that no money has been created, that only the intended recipients spend UTXO, etc. Bitcoin has its own powerful custom scripting language, enough to allow developers to create complex and custom transaction types. There are about five standard transaction types accepted by standard Bitcoin clients. However, there are other Bitcoin clients that will accept other types of transactions for a fee.